How to make the picture appear clearer on the LED big screen - the color is more vivid

Na Vincent Optoelectronics introduces you to two LED large screen brightness control methods.

The first method is to change the current flowing through the LED. Generally, the LED tube allows the continuous operating current to be around 20 mA. In addition to the saturation of the red LED, the brightness of the other LEDs is substantially proportional to the current flowing through;

The second method: the method uses the visual inertia of the human eye, and uses the pulse width modulation method to realize the gray scale control, that is, periodically changes the light pulse width (ie, the duty ratio) as long as the period of repeated repetition is short enough ( That is, the refresh frequency is high enough) that the human eye does not feel that the illuminating pixels are shaking. Since pulse width modulation is more suitable for digital control, in today's widespread use of microcomputers to provide LED display content, almost all LED large screens use pulse width modulation to control gray levels.

The control system of the LED display usually consists of three main parts: the main control box, the scanning board and the display control device. The main control box obtains the brightness data of each layer of pixels from the display card of the computer, and then re-allocates the data to a plurality of scanning boards, each of which is responsible for controlling several rows (columns) on the LED screen, and each row (column) The display control signals of the upper LEDs are transmitted in a serial manner. At present, there are two ways of serially transmitting display control signals: one is to control the gray level of each pixel point on the scanning board, and the scanning board decomposes the brightness values ​​of the pixels in each row from the control box (ie, pulse width modulation). Then, the turn-on signals of the LEDs of each row are serially transmitted to the corresponding LEDs in a pulse form (lighting is 1 and not lit to 0) to control whether they are lit. This method uses fewer devices, but the amount of data transmitted serially is larger because each pixel requires 16 pulses at 16 levels of gray during a repeated lighting period, requiring 256 levels of gray. 256 pulses, due to the device operating frequency limit, generally only make the LED large screen to achieve 16 gray levels.

Another method is that the serial transmission of the scan board is not the switching signal of each LED but an 8-bit binary luminance value. Each LED has its own pulse width modulator to control the lighting time. Thus, in a period of repeated lighting, each pixel point requires only 4 pulses in 16-level gray scale, and only 8 pulses in 256-level gray scale, which greatly reduces the serial transmission frequency. With this method of controlling the large screen gray scale of the LED, it is convenient to realize 256-level gray scale control.